Mixing device



April 22, 1956 J. K. CbMPTON 2,831,666

MIXING DEVICE Filed 001;. 19, 1956 IN V EN TOR.

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Wow 1" MIXTNG DEVICE Jack K. Compton, Dayton, Ohio Application October19, 1956, Serial No. 617,296

7 Claims. (Cl. 2611) (Granted under Title 35, U. S. Code (1952), sec.266) The invention described herein may be manufacured and used by orfor the United States Government for governmental purposes withoutpayment to me of any royalty thereon.

This invention relates to a device for mixing a gas and a liquid and,more particularly, to a device that empicys ultrasonic oscillations tomix a liquid and a gas.

in mixing a gas and a liquid such as air and fuel for a jet engine, itis desired that there be optimum distribution of the fuel throughout theair. However, the large quantity of fuel required by a jet engineresults in the fuel flowing at a rapid rate so that only a minimumperiod of time exists for mixing. This presents a problem when it isdesired that the distribution of the fuel throughout the air be at anoptimum. Obviously, if there is not sufficient mixture of the fuel andair, the mixture must be fuel rich in order to insure combustion withinthe jet engine. The present invention satisfactorily solves this problemby creating oscillations of an ultrasonic frequency to break down thestability of the liquid whereby the liquid mixes with the gas at anoptimum. The particular ultrasonic frequency, of course, depends on thestability of the liquid and the amount of mixing desired.

An object of the present invention is to provide a device for optimummixing of rapidly flowing liquid and a gas in a minimum of time.

Another object of this invention is to provide a device for mixing of aliquid and a gas at an ultrasonic freuency.

Other objects of this invention will be readily perceived from thefollowing description.

This invention relates to a device for mixing a liquid and a gascomprising a resonant chamber to which liquid as are supplied. Thequantity of liquid supplied to the resonant chamber is regulated. Theresonant chamber creates oscillations in the ultrasonic range to mix thegas and the liquid. Suitable means connect the outlet of the resonantchamber with an open ended tube, which is in resonant frequency with theoscillations in the resonant chamber. The connecting means matches theresonant chamber with the open ended tube whereby there is a maximumtransfer of energy therebetween.

The attached drawing illustrates preferred embodiments of the invention,in which:

Fig. l is a sectional view partly in elevation of one form of the mixingdevice of. the present invention; and

Fig. 2 is a sectional view partly in elevation of another embodiment ofthe mixing device of the present invention.

Referring to the drawing and particularly Fig. 1, there is shown amixing chamber 10 havin an opening 11 through which a gas, such as air,is supplied under pressure. The mixing chamber has a second opening 12through which a liquid, such as fuel, is supplied in a predeterminedquantity. The liquid is supplied to the mixing chamber ill from acylinder is of a liquid metering valve. The cylinder is has an inlet :5transverse to ll Ll Zfifififili Patented Apr. 22, 1958 c t i its axis.The inlet 15 is connected to a liquid source 16 under suitable pressureto permit liquid to enter the cylinder 14 through the inlet 15 and thento be pumped from the cylinder through its outlet and the opening l2into the mixing chamber 19. A piston or plunger 17, which moves withinthe cylinder 14, is preferably connected to a solenoid 18 although thepiston could be driven mechanically, if desired. The solenoid may beeither the electromagnetic or electrostatic or piezo-electric type; itis only necessary that the solenoid create a reciprocating action by thepiston 17 with the cylinder 14.

The metering of the liquid into the mixing chamber through the opening12 creates some mixing of the liquid and the gas before it flows fromthe mixing chamber 16 through its outlet 19 into a resonant chamber,which is preferably a rotating drum or cylinder 20 having a plurality ofopenings El in its wall. The openings 21 are designed to createoscillation of ultrasonic frequencies on the mixture of liquid and gasflowing therethrough into the interior of the drum 20.

The drum 2% is driven by a motor 22 connected thereto by a shaft 23. Themotor may be either pneumatic or mechanical or electrical as desired.The speed of the rotating drum 29 is such that it generates transverseand longitudinal waves at an ultrasonic frequency such as 25 kilocyclcs,for example. The frequency may be changed by varying the speed of therotating drum 2% or the number of openings 21; an increase in the speedof the drum or the number of openings increases the frequency. Theoutlet 24 of the rotating drum 20 communicates with an open endedtubular member 25 through a connecting passage 26. The passage 26 is anexponential flare, which means that the cross-sectional area of thepassage 26 increases exponentially with distance from its inlet adjacentthe outlet 24 of the drum 20, that matches the frequency generated bythe drum to free space. The design of the passage 26 as an exponentialflare permits transition of the resonant frequency waves generated inthe rotating drum 2!) to the open ended tube 25, which is in resonantfrequency with the oscillations produced within the drum 20, withminimum attenuation. The minimum requirement for the largest portion ofthe passage 26 is that the circumference at the largest portion is equalto at least one wavelength of the lowest frequency to be produced withinthe drum 20. In order to obtain the maximum wave amplitude for optimummixing of the liquid and the gas, the drum 2% is designed to have alength equal to an odd quarter wavelength.

Considering the operation of the mixing device of Fig. l, the gas issupplied to the mixing chamber 10 through the opening 11 at a greaterpressure than exists at the outiet of the open ended tubular member 25.The liquid is metered into the mixing chamber 1d through the opening 12.The amount of liquid entering the mixing chamber 10 may be varied byvarying the stroke of the piston 17, which is accomplished by varyingthe amplitude of the solenoid 18, or by varying the frequency of thepiston stroke, which is accomplished by varying the frequency of thesolenoid 18, or by varying both. The quantity of liquid metered into themixing chamber 10 could also be varied by varying the pressure in theliquid source 16 but such does not produce a simultaneous change as doesvarying the stroke or frequency of the stroke of the piston 17. Primarybreakdown of the liquid occurs within the mixing chamber 10 after it ismetered into the chamber.

As the mixture flows from the mixing chamber 10 through its outlet 19into the rotating drum 20, the shape of the openings 21 in the drum 2tand the speed at which the drum is rotating create oscillations of anultrasonic frequency on the mixture to thereby breakdown the stabilityof the liquid. The particular frequency selected depends on thestability of the liquid and the amount of mixing desired. The greaterthe flow of the mixture through the openings 21 in the drum 2%, thegreater the amplitude of the Waves; an increase in the amplitude of thewaves increases the mixing. Thus, an increase in size of the openings 21increases the am plitude of the waves and, thereby, increases mixing ofthe liquid and gas. The mixture of liquid and gas flows from therotating drum 2% through its outlet 2 into the passage 26 and the openended tubular member 25. By designing the passage 26 as an exponentialflare, as previously set forth, there is a maximum transfer of energyfrom the resonant chamber to the open ended tubular member 26.

While the mixing device of Fig. 1 may be employed with any pressuredifferential between the opening 11 in the mixing chamber and the outletof the open ended tubular member 26, the apparatus of Fig. 2 may beemployed only with a-specific fixed differential between the gasentering the device under pressure and the mixture leaving the device.In Fig. 2, the gas under pressure enters the resonant chamber Bill,which is fixed rather than rotating as in Fig. 1, through an opening oropenings 31. The resonant frequency of the chamber 30 depends on thepressure diiierential so that it is not necessary for the chamber to bemovable. The openings 31 are designed to create oscillations of anultrasonic frequency within the gas. The liquid is metered into theresonant chamber 30 through an opening or openings 32 by the meteringdevice of Fig. l, identified by the numeral 33 in Fig. 2. The openings32 are located a quarter of a Wavelength from the top of the resonantchamber. This is to insure that the liquid is metered into the resonantchamber 30 through the openings 32 at a pressure node. Since theresonant frequency of the resonant chamber 30 depends upon a pressuredifierential, which is fixed, the wavelength may be easily determined sothat the exact location of the opening or openings 32 may be easilycalculated. The resonant chamber 30 communicates with an open endedtubular member 34 through a passage 35. This passage is designed in theshape of an exponential flare so as to match the resonant chamber 30with the open ended tubular member The length of the tubular member 34is such that the tubular member 34 is in resonance with the frequencyexisting within the resonant chamber 30.

Considering the operation of the device of Fig. 2, th

gas under pressure flows into the resonant chamber 3! through theopening 31. As it passes through the opening 31, oscillations ofultrasonic frequency are created on the gas. The liquid is metered bythe metering device 33 into the resonant chamber 3% through the opening32. Since the opening 32 is located at a pressure node of the wavesbeing generated within the reso nant chamber 3!}, the liquid enters witha minimum of interference with the oscillations created by the gaspassing through the opening 31. These oscillations of the gas tend tobreakdown the liquid to thereby produce an optimum distribution of theliquid throughout the gas. The mixture flows from the resonant chamber30 into the open ended tubular member 34 with a minimum of attenuationdue to the passage 35 having an exponential flare.

An advantage of this invention is that the use of the mixing device withfuel and air as the liquid and gas would increase the efliciency of acombustion engine. The use of the mixing device of the present inventionwith jet engines would reduce the size and length of the burner andthereby reduce the overall engine size resulting in a substantialsaving.

For purposes of exemplification, particular embodiments of the inventionhave been shown and described according to the best presentunderstanding thereof.

However, it will be apparent that changes and modifications in thearrangement and construction of the parts thereof may be resorted towithout departing from the true spirit and scope of the invention.

1 claim:

1. A device for mixing a liquid and a gas comprising a mixing chamber,means to supply gas under pressure to the mixing chamber, means tointroduce a predetermined quantity of liquid into the chamber, arotating hollow drum connected to the outlet of the chamber andfunctioning as a resonant chamber, said drum having a plurality ofopenings in its wall, each of said openings separately communicatingwith the outlet of the mixing chamber during rotation of the drum toallow intermittent tlow of the mixture therethrough into the interior ofthe hollow drum to create oscillations of the mixture in the ultrasonicrange in the interior of the drum, said drum having an outlet in one endthereof, and an open ended tubular member communicating with the outletof the drum and in resonant frequency with the oscillations in theinterior of the drum.

2. A device for mixing a liquid and a gas comprising a mixing chamber,means to supply gas under pressure to the mixing chamber, means tointroduce a predetermined quantity of liquid into the mixing chamber, arotating hollow drum connected to the outlet of the chamber andfunctioning as a resonant chamber, said drum having a plurality ofopenings in its wall, each of said openings separately communicatingwith the outlet of the mixing chamber during rotation of the drum toallow intermittent flow of the mixture therethrough into the interior ofthe hollow drum to create oscillations of the mixture in the ultrasonicrange in the interior of the drum, said drum having an outlet in one endthereof, an open ended tubular member in resonant frequency with theoscillations in the drum, and means including a passage connecting theoutlet of the drum with the open ended tubular member, said passagehaving its crosssectional area increasing exponentially with distancefrom the outlet of the drum to the open ended tubular member whereby themixture flows from the drum to the tubular member with a maximumtransfer of energy.

3. A device for mixing a liquid and a gas comprising a mixing chamber,means to supply gas under pressure to the mixing chamber, means tointroduce a predetermined quantity of liquid into the mixing chamber, arotating hollow drum connected to the outlet of the chambar andfunctioning as a resonant chamber, said drum having a plurality ofopenings in its wall, each of said openings separately communicatingwith the outlet of the mixing chamber during rotation of the drum toallow intermittent flow of the mixture therethrough into the interior ofthe hollow drum to create oscillations of the mixture in the ultrasonicrange in the interior of the drum, said drum having an outlet in one endthereof, an open ended tubular member in resonant frequency with theoscillations in the drum, and means including a passage connecting theoutlet of the drum with the open ended tubular member, said passagehaving its crosssectional area increase with distance from the outlet ofthe drum to the open ended tubular member and the largestcross-sectional area of the passage having a circumference equal to atleast one wavelength of the lowest frequency produced in the drum.

4. A device for mixing a liquid and a gas comprising a mixing chamber,means to supply gas under pressure to the mixing chamber, means tointroduce a predetermined quantity of liquid into the mixing chamber, ato tating cylindrical hollow drum connected to the outlet of the mixingchamber and having its axis of rotation substantially perpendicular tothe axis of the outlet of the mixing chamber, said drum having aplurality of openings circumferentially disposed in its wall, each ofsaid openings separately communicating with the outlet of the mixingchamber during rotation of the drum to allow intermittent flow of themixture therethrough into the interior of the hollow drum to createoscillations of the mixture in the ultrasonic range in the interior ofthe rum, one end of the drum having an outlet therein for the flow ofthe mixture therefrom.

5. A device according to claim 4 in which the length of the drum isequal to an odd quarter wavelength of the frequency produced within theinterior of the drum.

6. A device for mixing a liquid and a gas comprising a mixing chamber,means to supply gas under pressure to the mixing chamber, means tointroduce a predetermined quantity of liquid into the mixing chamber, arotating cylindrical hollow drum connected to the outlet of the mixingchamber and having its axis of rotation substantially perpendicular tothe axis of the outlet of the mixing chamber, said drum having aplurality of openings circumferentially disposed in its wall, each ofsaid openings separately communicating with the outlet of the mixingchamber during rotation of the drum to allow intermittent flow of themixture therethrough into the interior of the hollow drum to createoscillations of the mixture in the ultrasonic range in the interior ofthe drum, one end of the drum having an outlet therein for the flow ofthe mixture therefrom, an open ended tubular member in resonantfrequency with the oscillations in the interior of the drum, and meansincluding a passage connecting the outlet of the drum with the openended tubular member, said passage having its cross sectional areaincrease exponentially with distance from the outlet of the drum to theopen ended tubular member whereby the mixture flows from the drum to thetubular member with a maximum transfer of energy.

7. A device for mixing a liquid and a gas comprising a mixing chamber,means to supply gas under pressure to the mixing chamber, means tointroduce a predetermined quantity of liquid into the mixing chamber, arotating cylindrical hollow drum connected to the outlet of the mixingchamber and having its axis of rotation substantially perpendicular tothe axis of the outlet of the mixing chamber, said drum having aplurality of openings circumferentially disposed in its wall, each ofsaid openings separately communicating with the outlet of the mixingchamber during rotation of the drum to allow intermittent flow of themixture therethrough into the interior of the hollow drum to createoscillations of the mixture in the ultrasonic range in the interior ofthe drum, one end of the drum having an outlet therein for the flow ofthe mixture therefrom, an open ended tubular member in resonantfrequency with the oscillations in the interior of the drum, meansincluding a passage connecting the outlet of the drum with the openended tubular member, said passage having its cross-sectional areaincrease with distance from the outlet of the drum to the open endedtubular member and the largest cross-sectional area of the passagehaving a circumference equal to at least one wavelength of th lowestfrequency produced in the drum.

References Cited in the file of this patent UNITED STATES PATENTS2,364,987 Lee Dec. 12, 1944 2,414,494 Vang Ian. 21, 1947 2,453,595Rosenthal Nov. 9, 1948 2,532,554 Joeck Dec. 5, 1950 2,650,617 WasserSept. 1, 1953 2,693,943 Fowle Nov. 9, 1954 2,697,581 Ray Dec. 21, 19542,745,372 Chertofi May 15, 1956 2,768,580 Parker Oct. 30, 1956

